1. Field of the Invention
The present invention relates to a vehicle mounted adaptor to which a portable radio transceiver, such as a hand-held mobile telephone or the like, is attached when used within a passenger compartment of a vehicle, and more specifically to such an adaptor which features an arrangement for recharging a backup battery provided in the transceiver.
2. Description of the Prior Art
In order to realize wider usage of a portable radio transceiver, it is a current tendency to design the transceiver in a manner to be attachable to a vehicle mounted adaptor when used in a passenger compartment of a vehicle. Thus, a portable transceiver subscriber is able to utilize his or her transceiver using power obtained from a car battery instead of a battery which has been installed in the transceiver. This is very advantageous from the battery power saving point of view in that the battery in the transceiver is of relatively limited power capacity. Further, the battery provided in the transceiver can be recharged while the transceiver is attached to the adaptor.
Before turning to the present invention it is deemed advantageous to discuss, with reference to FIG. 1, a known adaptor of the nature mentioned above.
FIG. 1 is a block diagram schematically showing a vehicular adaptor 10 and a portable radio transceiver 11. This transceiver 11 is operatively attached to the adaptor 10 when used within a passenger compartment of a vehicle. As shown, the adaptor 10 includes a power switch 12, a voltage regulator 14, a battery charger 16, and a hands free (viz., speakerphone) circuit 18. A car battery 20 has a minus terminal grounded and a plus terminal coupled to a common terminal 12a of the power switch 12 via a terminal 22a. The hands free circuit 18 is coupled to a loudspeaker 24 and a microphone 26 by way of terminals 28a, 28b, respectively. A terminal 22b of the adaptor 10 is grounded.
The power switch 12 is switched over from OFF position to ON position when a control signal C1 is applied thereto from the transceiver 11. The control signal C1 will be mentioned later. The voltage regulator 14 serves to lower a car battery voltage (12 volts for example) to a potential suitable for use in the transceiver 11. The voltage appearing at the output of the regulator 14 is maintained constant as is well known in the art. Each of the battery charger 16 and the hands free circuit 18, is configured in a manner well known to those skilled in the art and thus further descriptions thereof will be omitted for the sake of brevity.
The vehicular adaptor 10 is further provided with interface terminals 30a, 32a, 34a, 36a, 38a and 40a which are respectively coupled to counterparts 30b, 32b, 34b, 36b, 38b and 40b of the portable radio transceiver 11.
The transceiver 11 is further comprised of a power circuit 50, a main battery 52, a backup battery 54, a diode 56, a central processing unit (CPU) 58, a power switch circuit 60, a transmitter/receiver (TX/RX) section 62, and an antenna 64, all of which are coupled as illustrated.
The diode 56 is for preventing a direct current in the direction from the backup battery 54 to the main battery 52. The power switch circuit 60 includes a manually operated power switch 60a by which the operations of the transceiver 11 is initiated or terminated.
The ground or earth potential lines within the blocks 10, 11 are omitted merely for the sake of simplifying the drawing.
A portable mode of the transceiver 11 (viz., the transceiver 11 is used outside of a vehicle), will be described in brief. When the power switch 60a is turned on, it generates the above mentioned control signal C1 and another control signal C2. The CPU 58 responds to the control signal C2 and applies a control signal C3 to the power circuit 50 which, in response thereto, supplies the CPU 58 and the transmitter/receiver 62 with DC (direct current) power from the main battery 52. Thus, the portable transceiver 11 enters into an operation mode.
On the other hand, when the power switch 60a remains open in the portable mode, the main battery 52 continues to supply the CPU 58 and the power switch circuit 60 with DC power. Further, the main battery 52 serves to charge the backup battery 54. The power switch circuit 60 is ready to generate the control signals C1, C2. In the event that the main battery 52 is rendered inoperative due to over-discharging, the backup battery 54 initiates the DC power supply to the power switch circuit 60 and the CPU 58 in place of the main battery 52. This operation is not clear from FIG. 1, but, the instant invention is not directly concerned therewith and hence the detailed arrangements thereof are omitted for the sake of brevity.
On the contrary, in the event that the portable radio transceiver 11 is used within a vehicle compartment of a vehicle (viz., in-car mode), the transceiver 11 is coupled to the adaptor 10 as schematically illustrated in FIG. 1. The power switch 12 is switched over from OFF position to ON position in response to the control signal C1 which is generated upon the power switch 60a being turned on. Thus, the power circuit 50 receives DC power from the voltage regulator 14 and energizes the CPU 58 and the transmitter/receiver section 62. The transceiver 11 is usually designed such that the main battery 52 is prevented from supplying the power circuit 50 with DC power while the power circuit 50 is coupled to the voltage regulator 14. However, the present invention is not limited to such a transceiver design.
It is assumed that the main and backup batteries 52, 54 are both rendered inoperative due to over-discharging at the time when transceiver 11 is attached to the adaptor 10. In such a case, the power switch circuit 60 fails to issue the control signal C1 when the power switch 60a is turned on. This means that the power switch 12 is no longer switched over to the ON position even if the power switch 60a is turned on. As a result, the above mentioned prior art has encountered the problem in that the main battery 52 is undesirably required to be recharged using another suitable battery charger (not shown) in place of the vehicle mounted adaptor 10.